1. Field of the Invention
This invention is in the field of chemical process accelerator systems (U.S. Class 502/2, Int. Class B01J 35/00) comprising catalysts supported in high-shear-rate laminar flows created by Taylor Vortex Flows (TVF) and Circular Couette Flows (CCF) in a viscid fluid such as a reactant or an electrolyte in a chemical reactor or electrochemical cell.
2. Description of Related Art
Chemical process accelerator systems are used to increase or decrease speeds of chemical reactions or to selectively control intermediate reactions, compositions of final products or rates at which reactants are converted to final products or to electrical energy. They comprise two essential and cooperating components; namely, a) flow created in fluid reactant or electrolyte of a chemical reactor or electrochemical cell and b) a catalyst supported in the flow. The prior art teaches that the flow can be either turbulent or laminar.
Chemical processors require catalysts to promote reactions at acceptable commercial rates. Catalysts must be carefully engineered for a particular reaction or application. Although the prior art technologists consider catalysts as the most prominent constituents and they garner an overwhelming share of research investigation, catalysts are only one component of chemical process accelerator systems needed to achieve commercially viable reaction rates.
In their search for the catalyst equivalent of the Philosopher's Stone, researchers have examined numerous substances, metals, alloys, fabrication technologies and methodologies for forming and decorating catalysts and supporting structures. Nevertheless with few exceptions, improvements in catalyst performance have been modestly evolutionary rather than revolutionary. For example, prior art fuel cell catalysts have yet to break a longstanding barrier that will enable fuel cell electrodes to generate more than 1-Ampere per cm2 of electrode surface area over a long operating life without being poisoned by reactants or corroding to the point of uselessness.
In the case of electrochemical cells—and more specifically fuel cells, extensive research is now being conducted with half-cell analyses of a wide variety of catalysts; however, there is yet to be any significant improvement in fuel cell performance. One reason is that catalyst performance in these half cell experiments is focused on measuring Oxygen Reduction Reaction (ORR) rates for catalytic cathodes paired against either a Standard Hydrogen Electrode (SHE) or a Reversible Hydrogen Electrode (RHE). Because SHE and RHE half cell experiments are usually run at or near room temperature, at pressures of about 1-bar and with little or no fluid flow, they cannot replicate operating conditions in chemical reactors, such as fuel cells, where these parameters and intermediate reaction products will most certainly be different.
Factors that determine characteristics of catalytic compositions include the purpose of the chemical process, the method of operating the process and choices for reactant chemicals, temperatures, pressures, processing times, intermediate reactions, reaction byproducts capable of poisoning the catalysts, balance of plant (BOP) and other variables. But perhaps more important is the nature of reactions at and very near the surface of catalyst and these are heavily controlled by the characteristics of fluid flows at and near the catalyst surface where turbulence is either intended or a consequence of design (e.g. rough surfaces).
The rate at which catalytic chemical reactions proceed is restricted by two factors called a) transport-limiting and b) surface-limiting. Transport-limiting occurs because reactants are impeded in reaching or leaving catalyst sites. Surface-limiting occurs because of a tradeoff between the sum of reaction energies from primary and intermediate chemicals, surface attraction of ions such as H+ and OH− and poisoning rates by reaction products, such as CO. In addition, there can be tradeoffs between transport-limited and surface-limited factors, such as how changes in flow rates and pressures that promote chemicals moving to or from catalyst sites can change concentrations of intermediate chemicals capable of adhering to the catalyst surfaces, poisoning catalysts or, at least, retarding reactions. Thus in conventional chemical reactors, catalyst compositions are often designed to optimize results by making appropriate tradeoffs.